Update docs, add thermal and hybrid integration test

[bbrelje]

Purpose

Expand integration test to include more airplanes Update docs to reflect OpenMDAO 3.0 dependency

Type of change

What types of change is it?

• Breaking change (non-backwards-compatible fix or feature)
• Documentation update
• Testing expansion

Testing

Adds new integration test covering thermal components.

Checklist

• [x] I have run unit and regression tests which pass locally with my changes
• [x] I have added new tests that prove my fix is effective or that my feature works
• [x] I have added necessary documentation

[bernardopacini]

When running the examples, I run into the following error message for the HybridTwin.py case:

Traceback (most recent call last):
  File "/usr/local/lib/python3.8/site-packages/openmdao/utils/options_dictionary.py", line 468, in __setitem__
    meta = self._dict[name]
KeyError: 'dynamic_simul_derivs'

During handling of the above exception, another exception occurred:

Traceback (most recent call last):
  File "HybridTwin.py", line 279, in <module>
    prob.driver.options['dynamic_simul_derivs'] = True
  File "/usr/local/lib/python3.8/site-packages/openmdao/utils/options_dictionary.py", line 472, in __setitem__
    self._raise(msg.format(name), exc_type=KeyError)
  File "/usr/local/lib/python3.8/site-packages/openmdao/utils/options_dictionary.py", line 263, in _raise
    raise exc_type(full_msg)
KeyError: "ScipyOptimizeDriver: Option 'dynamic_simul_derivs' cannot be set because it has not been declared."

Interestingly this also fails for the current master branch but with a different error:

Traceback (most recent call last):
  File "HybridTwin_thermal.py", line 416, in <module>
    print(nice_print_names[i]+': '+str(prob.get_val(thing,units=units[i])[0])+' '+str(units[i]))
  File "/usr/local/lib/python3.8/site-packages/openmdao/core/problem.py", line 397, in get_val
    val = self.model._get_val(name, units=units, indices=indices, get_remote=get_remote)
  File "/usr/local/lib/python3.8/site-packages/openmdao/core/system.py", line 4246, in _get_val
    abs_name, typ = name2abs_name(self, name)
  File "/usr/local/lib/python3.8/site-packages/openmdao/utils/name_maps.py", line 149, in name2abs_name
    if name in system._var_allprocs_prom2abs_list['output']:
TypeError: 'NoneType' object is not subscriptable

Given that the error is different on this PR, I am adding this here as these changes are changing the behavior.

The remaining examples run without issues.